Microorganism Shewanella putrefaciens can grow with a variety of terminal acceptors, including oxygen, nitrate, nitrite, TMAO, Fe(3+), Mn(4+), etc. Such diversity admits that synthesis of terminal reductases could be induced by applied acceptors. To study electron transport chain of S. putrefaciens, we used low temperature EPR spectroscopy at different frequencies. It has been shown that, depending on the accessible electron acceptor studied, the microorganism developed different electron carriers. The growth with Fe(3) as the terminal electron acceptor induced the appearance of multiheme cytochromes type 2 low (ca 10 kD) and high (70 kD) molecular weight. Both cytochromes have four heme groups per protein molecule. We use low temperature EPR spectroscopy to study interactions between heme groups in the same protein molecule. [unreadable]